Allocation of radio resource in orthogonal frequency division multiplexing system

ABSTRACT

An uplink capacity is increased by a method in which more than two mobile stations simultaneously use a radio resource allocated to one mobile station. A method of allocating a radio resource in an orthogonal frequency division multiplexing system comprises receiving data associated with a radio resource allocation map from a base station, wherein the radio allocation map comprises control parameters for transmitting uplink data to the base station. The control parameters comprises orthogonal pilot pattern indicator for using orthogonal pilot patterns associated with supporting at least concurrent dual transmission by at least one mobile station, and for use in the same frequency band and same time duration. The orthogonal pilot patterns comprises at least a minus pilot being used for an uplink basic allocation unit. The mobile station then transmits uplink data to the base station by using the orthogonal pilot patterns.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application Nos.10-2004-0048436, 10-2004-0053139, 10-2004-0118087, filed on Jun. 25,2004, Jul. 8, 2004 and Dec. 31, 2004, respectively, the contents ofwhich are hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to an OFDMA (Orthogonal Frequency DivisionMultiplexing Access) type system, and particularly, to allocation ofradio resources in the OFDMA system.

BACKGROUND OF THE INVENTION

In an OFDM system, a high speed serial signal is divided into severalparallel signals and are modulated using orthogonal sub-carriers fortransmission and reception. Therefore, the orthogonal sub-carrierdivided into narrow bandwidths undergoes a flat fading and accordinglyhas excellent characteristics for a frequency selective fading channel.Since a transmitting device maintains orthogonality between sub-carriersby using a simple method such as a guard interval interleaving, areceiving device does not need a complicated equalizer or a rakereceiver generally used in a DS-CDMA (Direct Sequence-Code DivisionMultiplexing Access) method. The OFDM system with such advancedcharacteristics has been adopted as a standardized modulation type in aradio LAN, such as IEEE802.11a or HIPERLAN, and a fixed broadbandwireless access, such as IEEE802.16. The OFDM system has once beeninvestigated as one of applicable technologies of a modulation anddemodulation/multiple access method in a UMTS (Universal MobileTelecommunications system).

Recently, various multiple access methods based on the OFDM have beenactively researched. The OFDMA system has been actively investigated andstudied as a promising candidate technology for achieving a nextgeneration mobile communication satisfying with user requirementsremarkably enlarged such as an ultra high speed multimedia service. TheOFDMA system uses a two dimensional access method by coupling a timedivision access technology to a frequency division access technology.

FIG. 1 illustrates an allocation of a radio resource according to theconventional art. Referring to FIG. 1, in a radio communications system,many users divide and use limited uplink/downlink radio resources.However, many users do not divide and use a radio resource that isallocated to one user. That is, there may not exist any method in whichthe same resource is allocated to two or more users.

For instance, in a TDMA (Time Division Multiplexing Access) system, acertain time interval is allocated to a user, and accordingly ascheduling is carried out such that only the user can use radioresources in the specific allocated time interval. In a CDMA (CodeDivision Multiplexing Access) system, the scheduling is also carried outso as to allocate a difference code for each user. In other words, onecode is allocated to only one user. In the OFDM/OFDMA system, a certainuser can use an allocated region that comprises a two dimensional maprepresented by time and frequency.

FIG. 2 illustrates a data frame configuration according to aconventional OFDM/OFDMA radio communications system. Referring to FIG.2, a horizontal axis indicates time by a symbol unit, while the verticalaxis indicates frequency by a subchannel unit. The subchannel refers toa bundle of a plurality of sub-carriers.

An OFDMA physical layer divides active sub-carriers into groups, and theactive sub-carriers are transmitted to different receiving endsrespectively by the group. Thus, the group of sub-carriers transmittedto one receiving end is referred to as the subchannel. The sub-carriersconfiguring each subchannel may be adjacent to one another or an equalinterval away from one another.

In FIG. 2, slots allocated to each user are defined by a data region ofa two dimensional space and refers to a set of successive subchannelsallocated by a burst. One data region in the OFDMA is indicated as arectangular shape which is determined by time coordinates and subchannelcoordinates. This data region may be allocated to an uplink of aspecific user or a base station can transmit the data region to aspecific user over a downlink.

A downlink sub-frame is initiated by a preamble used for synchronizationand equalization in a physical layer, and subsequently defines anoverall frame structure by a downlink MAP (DL-MAP) message and an uplinkMAP (UL-MAP) message both using a broadcasting type which defineposition and usage of a burst allocated to the downlink and the uplink.

The DL-MAP message defines a usage of a burst allocated with respect toa downlink interval in a burst mode physical layer. The UL-MAP messagedefines a usage of a burst allocated with respect to an uplink intervaltherein. An information element (IE) configuring the DL-MAP includes aDIUC (Downlink Interval Usage Code), a CID (Connection ID) andinformation of a burst location (for example, subchannel offset, symboloffset, the number of subchannels and the number of symbols). A downlinktraffic interval of a user side is divided by the IE.

Alternatively, a usage of an IE configuring the UL-MAP message isdefined by a UIUC (Uplink Interval Usage Code) for each CID, and alocation of each interval is defined by a ‘duration’. Here, a usage byan interval is defined according to the UIUC value used in the UL-MAP,and each interval begins at a point as far as the ‘duration’ defined inthe UL-MAP IE from a previous IE beginning point.

DCD (Downlink Channel Descriptor) message and UCD (Uplink ChannelDescriptor) message refer to physical layer related parameters to beapplied to each burst interval allocated to the downlink and the uplink,which include a modulation type, a FEC code type, and the like. Inaddition, Parameters required (e.g., K and R values of R-S code) aredefined according to various downlink error correction code types. Suchparameters are provided by a burst profile defined for each UIUC andDIUC within the UCD and the DCD.

On the other hand, a MIMO (Multi-input Multi-output) technique in theOFDM/OFDMA system is classified into a diversity method and amultiplexing method. The diversity method is a technique in whichsignals having undergone different rayleigh fading are coupled to oneanother by a plurality of transmitting/receiving antennas to compensatea channel deep between paths, thereby leading to an improvement ofreception performance. A diversity benefit to be obtained by thistechnique is divided into a transmission diversity and a receptiondiversity depending on whether it is a transmitting end or a receivingend. When N-numbered transmitting antennas and M-numbered receivingantennas are provided, a maximum diversity benefits corresponds to MN bycoupling MN-numbered individual fading channels in maximum.

The multiplexing method increases a transmission speed by makinghypothetical subchannels between transmitting and receiving antennas andtransmitting respectively different data through each transmittingantenna. Unlike the diversity method, the multiplexing method cannotachieve sufficient benefits when only one of transmitting and receivingends uses a multi-antenna. In the multiplexing method, the number ofindividual transmission signals to be simultaneously transmittedindicates the multiplexing benefit, which is the same as a minimum valueof the number of transmitting end antennas and the number of receivingend antennas.

There also exists a CSM (Collaborative Spatial Multiplexing) method asone of the multiplexing method. The CSM method allows two terminals touse the same uplink, thereby saving uplink radio resources.

Methods for allocating radio resources of the uplink or downlink in theOFDM/OFDMA system, namely, allocating data bursts are divided into atypical MAP method and an HARQ method according to whether the HARQmethod is supported or not.

In the method for allocating the bursts in the general downlink MAP,there is shown a square composed of a time axis and a frequency axis. Inthis method, an initiation symbol offset, an initiation subchanneloffset, the number of symbols used and the number of subchannels usedare informed. A method for allocating the bursts in sequence to a symbolaxis is used in the uplink, and accordingly, if the number of symbolsused is informed, the uplink bursts can be allocated.

The HARQ MAP, unlike the general MAP, uses a method for allocating theuplink and the downlink in sequence to a subcarrier axis. In the HARQMAP, only the length of burst is informed. By this method, the burstsare allocated in sequence. An initiation position of the burst refers toa position where the previous burst ends, and the burst takes up radioresources as much as the length allocated from the initiation position.The OFDM/OFDMA system supports the HARQ using the HARQ MAP.

In the HARQ MAP, a position of the HARQ MAP is informed by an HARQ MAPpointer IE included in the DL-MAP. Accordingly, the bursts are allocatedin sequence to the subchannel axis of the downlink. The initiationposition of the burst refers to the position where the previous burstends and the burst takes up radio resources as much as the lengthallocated from the initiation position. This is also applied to theuplink.

FIG. 3 illustrates an uplink radio resource (data burst) that isallocated to a terminal using a typical DL-MAP according to aconventional art.

In case of a typical DL-MAP, a first burst subsequent to a position ofthe UL-MAP is allocated to the terminal. The UL-MAP allocates an uplinkdata burst by the UL-MAP IE.

In the CSM method of the OFDMA technique based on IEEE802.16d and e, abase station in the typical DL-MAP method informs each terminal of databurst positions by a MIMO UL basic IE with the data format as shown inTable 1, and allocates the same radio resource to each terminal.

In order to notice the use of the MIMO UL basic IE, UIUC=15 is used asan extended UIUC. There are 16 different values to be represented as theextended UIUC.

TABLE 1 Size Syntax (bits) Notes MIMO_UL_Basic_IE( ){ Extended DIUC 4MIMO = 0x02 Length 4 Length of the message in bytes(variable) Num_Assign4 Number of burst assignment For(j=0; j<Num_assign;j++){ CID 16 SS basicCID UIUC 4 MIMO_Control 1 For dual transmission capable MSS 0: STTD 1:SM For Collaborative SM capable MSS 0: pilot pattern A 1: pilot patternB Duration 10 In OFDMA slots } }

The MIMO UL basic IE which is used for allocating the same uplinkresource to two terminals is used for other conventional MIMOs. When aterminal has more than two antennas, the MIMO UL basic IE informs theterminals which method, namely, a STTD method for obtaining a diversitybenefit or an SM method for increasing transmission speed, is used.

The CSM method in the OFDMA technique based on IEEE 802.16d, e can beembodied by the HARQ MAP for an HARQ embodiment. FIG. 4 illustrates anuplink radio resource (data burst) that is allocated to a terminal byusing the HARQ-MAP according to a conventional art.

Unlike the method for informing every bursts by the DL-MAP, in themethod as shown in FIG. 4, an HARQ existence is informed by an HARQ MAPpointer IE of the DL-MAP IE for an HARQ exclusive. The HARQ MAP pointerIE informs of a modulation of the HARQ MAP, and coding state and size ofthe HARQ MAP.

The HARQ MAP is composed of a compact DL-MAP/UL-MAP informing ofposition and size of the HARQ burst, and, in particular, uses a MIMOcompact UL IE for the MIMO. The MIMO compact UL IE is used by beingattached to a position subsequent to a ‘compact UL-MAP IE for normalsubchannel’ for allocating the conventional subchannel and a ‘compactUL-MAP IE for band AMC’ for allocating the band AMC. As shown in FIG. 4,the MIMO compact UL IE has only a function of a previously allocatedsubchannel.

In the aforementioned conventional art, when additional radio resourceis required by the increased demand of the uplink, there is noappropriate way to satisfy such requirement. In that case, adding afrequency resource may be considered. However, because a base stationposition must be considered and it affects on the entire system, it isnot regarded as a preferred alternative for increasing uplink resources.More preferred method is to allow more than two user to simultaneouslyuse the existing resources that are previously allocated to one user.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a method forallocating a radio resource in an OFDM/OFDMA system in which many userscan simultaneously take up and use a radio resource allocated from anuplik.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a radio resource allocation system in an orthogonalfrequency multiplexing access system, in which the same uplink radioresource is allocated to more than two terminals.

According to one embodiment of the invention, a method of allocating aradio resource in a wireless communication system utilizing orthogonalfrequency division multiplexing comprises receiving data associated witha radio resource allocation map from a base station. The radioallocation map comprises control parameters for transmitting uplink datato the base station. The control parameters comprises orthogonal pilotpattern indicator for using orthogonal pilot patterns associated withsupporting at least concurrent dual transmission by at least one mobilestation, and for use in the same frequency band and same time duration.The orthogonal pilot patterns comprising at least a minus pilot beingused for an uplink basic allocation unit. The mobile station thentransmits uplink data to the base station by using the orthogonal pilotpatterns. Preferably, the at least concurrent dual transmission isachieved by using at least two antennas in the mobile station.

According to one aspect of the invention, each one of the orthogonalpilot patterns comprises a plus pilot and the minus pilot located ateach diagonal corner of the uplink basic allocation unit. Preferably,the plus pilot and the minus pilot have opposite phases.

According to another aspect of the invention, information associatedwith the orthogonal pilot patterns is communicated to the mobile stationusing a map information element or a HARQ map information element.

According to another aspect of the invention, the uplink data comprisesat least two sets of data spatially multiplexed onto the same subchannelby using the orthogonal pilot patterns.

According to another embodiment of the invention, a method of allocatinga radio resource in an orthogonal frequency division multiplexing systemcomprises transmitting, to a mobile station, data associated with aradio resource allocation map, wherein the radio allocation mapcomprises control parameters for transmitting uplink data to the basestation, wherein the control parameters comprises orthogonal pilotpattern indicator for using orthogonal pilot patterns associated withsupporting at least concurrent dual transmission by at least one mobilestation, and for use in the same frequency band and same time duration,the orthogonal pilot patterns comprising at least a minus pilot beingused for an uplink basic allocation unit; and receiving uplink data fromthe mobile station, wherein the uplink data is coded using theorthogonal pilot patterns. Preferably, the concurrent dual transmissionis achieved by using at least two antennas in the mobile station, andthe uplink data comprises at least two sets of data spatiallymultiplexed onto the same subchannel by using the orthogonal pilotpatterns.

According to one aspect of the invention, each one of the orthogonalpilot patterns comprises a plus pilot and the minus pilot located ateach diagonal corner of the uplink basic allocation unit. Preferably,the plus pilot and the minus pilot have opposite phases.

According to another aspect of the invention, information associatedwith the orthogonal pilot patterns is communicated to the mobile stationusing a map information element or a HARQ map information element.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 illustrates an allocation of a radio resource according to aconventional art.

FIG. 2 illustrates a data frame configuration in a conventional OFDMAradio communications system.

FIG. 3 illustrates an operation of allocating an uplink radio resourceto a terminal by using a typical DL-MAP according to conventional art.

FIG. 4 illustrates an operation of allocating an uplink radio resourceto a terminal by using an HARQ-MAP according to conventional art.

FIG. 5 illustrates an allocation of an uplink radio resource in anOFDM/OFDMA system according to a first embodiment of the presentinvention.

FIG. 6 illustrates a basic allocation unit for an uplink radio resourcewhich is transmitted through an uplink in an OFDM/OFDMA system.

FIG. 7A illustrates pilot patterns for multi-users according to thefirst embodiment of the present invention.

FIG. 7B illustrates pilot patterns using different orthogonal codesaccording to another embodiment of the present invention.

FIG. 7C is a signal value table allocated to each pilot shown in FIGS.7A and 7B.

FIG. 8 illustrates a combination of pilot patterns configuring an uplinkdata burst according to one embodiment of the present invention.

FIG. 9 illustrates an operation based on a CSM method using a typicalDL-MAP in accordance with one embodiment of the present invention.

FIG. 10 illustrates an operation based on a CSM method using an HARQ-MAPin accordance with one embodiment of the present invention.

FIG. 11 illustrates an operation based on the CSM method using theHARQ-MAP in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Hereinafter, preferred embodiments of the present inventionwill be explained with reference to the accompanying drawings asfollows.

The present invention is a technology for enlarging uplink capacity,which allows many mobile terminals to simultaneously use a radioresource allocated to one mobile terminal. A mobile terminal requires avariation of a pilot or a reference signal for measuring radio channels,while a base station requires a method for decoding data (or signals) ofa plurality of mobile terminals transmitted using one radio resource anda method for controlling power to reduce an affect of a signalinterference due to an increase of users.

FIG. 5 illustrates an uplink radio resource allocation in an OFDM/OFDMAsystem, according to one embodiment of the present invention, in whichit is assumed that the same radio resource is allocated to user 1 anduser 5 for reference. The term “user” represents a mobile terminal.

A base station first informs the two users (user 1 and user 5) by asignaling or a message that the same radio resource is allocatedthereto, and information related to types of channel coding to be used,coding rate, modulation method, pilot pattern, code system for space andtime, and other parameters.

A signal transmission/reception between mobile terminals and a basestation of the two users (for example, user 1 and user 5) has fourdifferent transmission/reception combinations, respectively, accordingto the code system for space and time, the number of receiving antennasof the base station, and the number of transmitting antennas of themobile terminals, which will be explained as follows.

First, under a spatial multiplexing transmission method, when the mobileterminals of the two users (user 1 and user 5), respectively, have onetransmitting antenna and the base station has more than two receivingantennas, the transmission/reception combination is defined in [Equation1] as follows.

$\begin{matrix}{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{n}\end{bmatrix} = {{\begin{bmatrix}h_{11} & h_{12} \\h_{21} & h_{22} \\\vdots & \vdots \\h_{N\; 1} & h_{N\; 2}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2}\end{bmatrix}} + v}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In [Equation 1], x_(i) is a signal transmitted to an i^(th) antenna,h_(ji) is a channel which is delivered from an i^(th) mobile terminal toa j^(th) antenna of the base station, s_(i) is data of the i^(th) mobileterminal, and v is an additive White Gaussian Noise Vector (AWGNVector).

Second, under the spatial multiplexing transmission method, when themobile terminals of the two users (user 1 and user 5) respectively haveone transmitting antenna and the base station has one receiving antenna,the transmission/reception combination is defined in [Equation 2] asfollows.

x=h ₁ s ₁ +h ₂ s ₂ +v  [Equation 2]

In [Equation 2], x is a signal transmitted to the base station, h_(i) isa channel delivered from an i^(th) mobile terminal to the base station,s_(i) is data of the i^(th) mobile terminal, and v is an additive WhiteGaussian Noise Vector (AWGN Vector).

Third, under a space time transmit diversity transmission method, whenthe mobile terminals of the two users (user 1 and user 5) respectivelyhave two transmitting antennas and the base station has more than tworeceiving antennas, the transmission/reception combination is defined in[Equation 3] as follows.

$\begin{matrix}{\begin{bmatrix}{x_{1}(k)} \\{x_{1}^{*}\left( {k + 1} \right)} \\{x_{2}(k)} \\{x_{2}^{*}\left( {k + 1} \right)}\end{bmatrix} = {{\begin{bmatrix}h_{1,11} & h_{1,12} & h_{2,11} & h_{2,12} \\h_{1,12}^{*} & {- h_{1,11}^{*}} & h_{2,12}^{*} & {- h_{2,11}^{*}} \\h_{1,21} & h_{1,22} & h_{2,21} & h_{2,22} \\h_{1,22}^{*} & {- h_{1,21}^{*}} & h_{2,22}^{*} & {- h_{2,21}^{*}}\end{bmatrix}\begin{bmatrix}s_{1,1} \\s_{1,2} \\s_{2,1} \\s_{2,2}\end{bmatrix}} + v}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In [Equation 3], x_(i) is a signal transmitted to an i^(th) antenna ofthe base station, h_(i,jk) is a channel delivered from a k^(th) antennaof an i^(th) mobile terminal to a j^(th) antenna of the base station,s_(i,j) is a j^(th) data of the i^(th) mobile terminal, and v is anadditive White Gaussian Noise Vector (AWGN Vector).

Fourth, under the spatial multiplexing transmission method, when themobile terminals of the two users (user 1 and user 5) respectively havea plurality of transmitting antennas and the base station has more thanfour receiving antennas, the transmission/reception combination isdefined in [Equation 4] as follows.

$\begin{matrix}{\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\x_{4}\end{bmatrix} = {{\begin{bmatrix}h_{1,11} & h_{1,12} & h_{2,11} & h_{2,12} \\h_{1,21} & h_{1,22} & h_{2,21} & h_{2,22} \\h_{1,31} & h_{1,32} & h_{2,31} & h_{2,32} \\h_{1,41} & h_{1,42} & h_{2,41} & h_{2,42}\end{bmatrix}\begin{bmatrix}s_{1,1} \\s_{1,2} \\s_{2,1} \\s_{2,2}\end{bmatrix}} + v}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In [Equation 4], x_(i) is a signal transmitted to an i^(th) antenna ofthe base station, h_(i,jk) is a channel delivered from a k^(th) antennaof an i^(th) mobile terminal to a j^(th) antenna of the base station,s_(i,j) is a j^(th) data of the i^(th) mobile terminal, and v is anadditive White Gaussian Noise Vector (AWGN Vector).

The base station transmits predetermined information (i.e., types ofchannel coding, coding rate, modulation method, pilot pattern, codesystem for space and time, etc) to the two users (user 1 and user 5),and determines priorities of the two users (user 1 and user 5). (here,it is assumed that the user 1 is a first user and the user 5 is a fifthuser)

Once determining each priority, the two users transmit respective datato the base station by including the data in sub-carriers for data of abasic allocation unit. The basic allocation unit is illustrated in FIG.6.

FIG. 6 illustrates a basic allocation unit (also known as a tile) of aradio resource transmitted through an uplink in an OFDM/OFDMA system. Amultiple of the basic allocation unit becomes a minimum allocation unitcapable of being allocated to one user. Six times of the basicallocation unit, as an example according to the conventional art, is theminimum allocation unit.

A frequency axis of the basic allocation unit can depend on an order ofsub-carriers, and be an axis configured by a group unit by making aplurality of sub-carriers which are extended (or adjacent) thereto agroup. The axis can be arbitrarily configured.

The basic allocation unit transmitted through an uplink in theOFDM/OFDMA system may have a different structure from that shown in FIG.6 and may have a different arrangement of the pilots and data inaccordance to the system characteristics. When using a different basicallocation unit from that shown in FIG. 6, pilot patterns suitabletherefor may be combined as shown in FIG. 8.

The base station analyzes a pilot pattern of the basic allocation unitreceived over the uplink to identify which user (i.e., mobile terminal)has transmitted the received data. In other words, the base stationidentifies whether the received data is from user 1 or user 5 byanalyzing the pilot pattern included in the basic allocation unit.

FIGS. 7A and 7B illustrate pilot patterns according to the firstembodiment of the present invention, and FIG. 7C is a table showing asignal value allocated to each pilot shown in FIGS. 7A and 7B.

In patterns 1, 2, and 3 as shown in FIG. 7A, user 1 and user 5 usedifferent pilots, respectively, and thus, the data of the two users canbe identified. On the other hand, in pattern 4 as shown in FIG. 7B, user1 and user 5 use the same pilot sub-carrier or subchannel, but the dataof the two users can be identified by using orthogonal codes.

For re-explaining these in aspect of a division method, pattern 1 ispilots according to a time division and a frequency division, pattern 2is pilots according to the frequency division, pattern 3 is pilotsaccording to the time division, and pattern 4 is pilots according to acode division.

The pilot patterns in FIGS. 7A and 7B show embodiments of the presentinvention, and may be changed according to the basic allocation unit.Furthermore, when the radio resource of the two users (user 1 and user5) is composed of a plurality of basic allocation units, as shown inFIG. 8, the patterns in FIGS. 7A to 7C can be combined.

Referring to FIG. 7C, the pilot patterns C and D according to oneembodiment of the present invention are illustrated. Because of theorthogonality, the pilot patterns C and D are used for mobile stationscapable of dual transmission, as noted in Table 4 below. The pilotsignal value of +1 represents a positive amplitude pilot, whereas thepilot signal value of −1 represents a negative amplitude pilot. In otherwords, +1 and −1 represents the pilots that are phase shifted by 180degrees.

Since pilots are used for compensating distortion due to a radiochannel, they should have a structure in which the pilots for user 1 andthe pilots for user 5 are alternate. The base station uses a pilotsignal for measuring the radio channel for each user and compensatingthe channel, and applies it to a method for dividing data of users. Inaddition, data for each user can be divided and detected by applying aradio channel of each user and the number of users for the simultaneousallocation, which has already been known, to an equation for a detectionmethod such as a maximum likelihood herebelow.

$\begin{matrix}{x = {{{h_{1}s_{1}} + {h_{2}s_{2}} + {v\left( {{\hat{s}}_{1},{\hat{s}}_{1}} \right)}} = {\underset{({s_{1},s_{2}})}{\arg \mspace{11mu} \max}{{x - {{\hat{h}}_{1}s_{1}} - {{\hat{h}}_{2}s_{2}}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Under the spatial multiplexing transmission method, [Equation 5]represents the maximum likelihood when the mobile terminals of the twousers (user 1 and user 5) respectively have one transmitting antenna,and the base station has one receiving antenna.

In [Equation 5], ĥ₁,ĥ₂ are estimation values of radio channelcoefficients h₁,h₂ obtained using pilots. The ĥ₁,ĥ₂ can be re-estimatedby using ŝ₁,ŝ₂, and the ŝ₁,ŝ₂ can be updated by using the re-estimatedĥ₁,ĥ₂. s₁,s₂ in [Equation 5] can have zero and a value of a modulationvalue, which has already been known. For instance, when the modulationmethod is a QPSK method, a set for values which the s₁,s₂ may have {1+i,1−i, −1+i, −1−i, 0}.

The base station controls power of the two users through a downlink suchthat signals of the two users (user 1 and user 2) can have appropriatepower. In some cases, the base station can control a whole power of thetwo users to be uniform and also control each signal power of the twousers. Explaining it in more detail, the base station controls powerP1+P5 obtained by adding the power P1 of the user 1 and the power P5 ofthe user 5 to be maintained as same as power P2, P3 or P4 of other users(user 2, user 3 or user 4), or controls the sum of power P1+P5 of thetwo users such that the sum of power P1+P5 can be maintained to bestronger or weaker than the power P3, P3 or P4 of other users.

On the other hand, in order to detect data of the two users moreprecisely, the base station may adjust a power ratio (P1:P5) between thetwo users. That is, a weight value is included in the power of one ofthe two users, so as to adjust the power ratio (P1:P5) between the twousers.

For instance, when the power ratio between the two users using the QPSKmethod is 1:4, signals added have different values, respectively, asshown in [Table 2] herebelow, and accordingly the detection is moreeasily performed.

TABLE 2 User2 User1 2 + 2i 2 − 2i −2 + 2i −2 − 2i 1 + i 3 + 3i 3 − i−1 + 3i −1 − i 1 − i 3 + i 3 − 3i −1 + i −1 − 3i −1 + i 1 + 3i 1 − i−3 + 3i −3 − i −1 − i 1 + i 1 − 3i −3 + i −3 − 3i

A user that cannot send data delivers a null value or a dummy code tothe base station. For instance, in the structure shown in FIG. 3, theuser sends 1+i by including it in eight sub-carriers for data.

Hereinafter, another embodiment of the present invention will beexplained.

When a terminal uses the CSM (Collaborative Spatial Multiplexing)method, the same uplink radio resource is allocated to two mobileterminals and different pilot patterns are used, respectively, foridentifying signals delivered from two mobile terminals. Applying theCSM method to the two terminals having two antennas is possible by thetypical DL-MAP and the HARQ MAP.

FIG. 9 illustrates an operation of the CSM method using the typicalDL-MAP according to an embodiment of the present invention.

In the typical UL-MAP, the UL-MAP allocates a first data burstsubsequent thereto to a terminal. The UL-MAP, as shown in FIG. 8,allocates the data burst by the UL-MAP IE.

In the CSM method, a position of the burst allocated to two mobileterminals is informed by a MIMO UL enhanced IE with a format as shown inTable 3, or the conventional MIMO UL basic IE.

Hereinafter, an embodiment of the CSM method by the MIMO UL enhanced IE,a new IE, will be explained. When every IEs to be represented as theUIUC is included, as shown in Table 3, a new extended UIUC can befabricated as 11 slots in order to add a new IE.

TABLE 3 UIUC Usage 0 Fast-Feedback Channel 1-10 Different burst Profiles11 New Extended UIUC 12 CDMA Bandwidth Request, CDMA ranging 13 PARPreduction allocation, Safety zone 14 CDMA Allocation IE 15 Extended UIUC

TABLE 4 Size Syntax (bits) Notes MIMO_UL_Enhanced_IE( ){ New ExtendedUIUC 4 Enhanced MIMO = 0x01 Length 4 Length of the message inbytes(variable) Num_Assign 4 Number of burst assignmentFor(j=0;j<Num_assign;j++){ Num_CID 2 For(i=0;i<Num_CID;i++){ CID 16 SSbasic CID UIUC 4 MIMO control 2 For dual transmission capable MSS 00:STTD/pilot pattern A, B 01: STTD/pilot pattern C, D 10: SM/pilot patternA, B 11: SM/pilot pattern C, D For Collaborative SM capable MSS with oneantenna. 00: pilot pattern A 01: pilot pattern B 10~11: reserved }Duration 10 In OFDMA slots } Padding variable }

In [Table 4], an uplink resource allocation is determined by a fieldvalue referred to as ‘duration’. The base station accumulates the numberof slots allocated to a time axis, unlike the resource allocation of asquare shape used in the downlink, and informs the accumulated value tothe terminal. At this time, the number of bursts to be used is informedby an ‘Num_assign’ field, and CIDs (Connection IDs) of the mobileterminal allocated to each burst are repeatedly informed by the basestation.

Characteristics of the bursts allocated to the mobile terminal arepreferably determined by a ‘MIMO control’ field. When the mobileterminal is registered in the base station for applying a CSM(Collaborative Spatial Multiplexing) which is one of MIMO modes, a CSMnegotiation between the mobile terminal and base station is performed soas to be known whether the CSM is possible to be applied. Accordingly,the CSM is applied to the mobile terminal for which the CSM is possible.

[Table 5] illustrates a structure of SBC request/response (REQ/RSP)messages exchanged between the base station and the mobile terminalduring the CSM negotiation.

TABLE 5 Type Length Value Xxx 1 bit Bit #0: Collaborative SM Bit #1-#7:reserved

When each of the two terminals has one antenna, the base stationidentifies two signals by referring to as A and B for the pilotpatterns. When each of the two terminals has two antennas, the basestation provides one terminal with pilot patterns A and B, whileproviding the other terminal with pilot patterns C and D.

As explained above, the “MIMO UL enhanced IE” message can be used by‘extended UIUC=11’. The “MIMO UL enhanced IE” message can be used bothwhen the terminal has only one antenna and when the terminal has twoantennas. The IE is characterized by simultaneously allocating twoterminals to one uplink burst which is uploaded to the base station. Asshown in FIG. 9, the uplink bursts (burst#1 and burst#2) allocated tothe two terminals are allocated by using one uplink.

Next, an embodiment of the CSM method by using the “MIMO UL basic IE”message will be explained. [Table 6] illustrates a data format of the“MIMO UL basic IE” message.

TABLE 6 Size Syntax (bits) Notes MIMO_UL_basic_IE( ){ Extended UIUC 4MIMO = 0x02 Length 4 Length of the message in bytes(variable) Num_Assign4 Number of burst assignment For(j=0;j<Num_assign;j++){ CID 16 SS basicCID UIUC 4 MIMO control 2 For dual transmission capable MSS 0: STTD 1:SM For Collaborative SM capable MSS 0: pilot pattern A 1: pilot patternB Duration 10 In OFDMA slots Pilot pattern 1 For Collaborative SM dualtransmission capable MSS 0: pilot pattern A B 1: pilot pattern C D }Padding variable }

The “MIMO UL basic IE” message used for allocating the same uplinkresource (data burst) from the base station to the two terminals is alsoused for other MIMOs. First, when each terminal has more than twoantennas, the base station informs the terminals by using the ‘MIMOcontrol’ field whether to use an STTD method for obtaining a diversitybenefit or an SM method for increasing transmission speed. In addition,when each terminal supports the CSM method, the base station allocatesthe same uplink resource to the two terminals by using the ‘MIMOcontrol’ field, and instructs the two terminals to use different pilotpatterns, respectively, in order to identifying signals transmitted formthe two terminals. In order to apply the present invention, when eachterminal has two antennas, the conventional ‘MIMO control’ field informsof the pilot patterns to be used by the two terminals by using one bitreserved for the CSM. There are A˜D pilot patterns, which are allocatedby two for each terminal.

Next, a CSM method using an HARQ-MAP, as a preferred embodiment of thepresent invention, will be explained as follows. Unlike the conventionalmethod for allocating a burst to a terminal by the DL-MAP, the HARQexistence is informed by an HARQ MAP pointer IE of the DL-MAP IE. TheHARQ MAP pointer IE informs of modulation and coding state of the HARQMAP and the size thereof.

The HARQ MAP having informed by the HARQ pointer IE is composed of aMIMO compact DL-MAP/UL-MAP which informs of position and size of an HARQburst. Preferably, a MIMO compact UL IE is used for determining a MIMOmode and a ‘MIMO compact UL IE for collaborative SM’ is used for theCSM.

FIG. 10 illustrates an operation of the CSM method using the HARQ-MAPaccording to an embodiment of the present invention. Table 7 shows adata format of the “MIMO compact UL MAP IE” message for the operation ofthe CSM method.

The “MIMO compact UL IE” message uses a ‘compact UL-MAP IE for normalsubchannel’ for allocating the conventional art subchannel and a‘compact UL-MAP IE for band AMC’ for allocating the band AMC. Becausethe same subchannel (uplink resource) should be allocated according tocharacteristics of the CSM, as shown in FIG. 10, the HARQ MAP allocatesthe same subchannel to two channels having a different connection factor(RCID), respectively. Moreover, in order to provide a function of theallocated region, the ‘MIMO compact UL IE for collaborative SM’ isattached to a position subsequent to the subchannel for use. A value of‘CSM_control’ is differentiated according to the number of antennas ineach terminal. That is, when each terminal uses only one antenna, thepilot pattern used by the two terminals is divided into A and B. Wheneach terminal uses two antennas, A and B are allocated to one terminaland C and D are allocated to the other terminal.

TABLE 7 Size Syntax (bits) Notes MIMO_compact UL-map IE( ){ CompactUL-MAP 3 Type = 7 UL-MAP Sub-type 5 CSM = 0x02 Length 4 Length of the IEin Bytes RCID_num 1 Number of CID allocated into the same regionFor(i=0; i<RCID_num: i++){ RCID_IE variable CSM control 1 ForCollaborative SM capable MSS with one antenna 0: pilot pattern A 1:pilot pattern B For Collaborative SM capable MSS with dual antennas 0:pilot pattern A, B 1: pilot pattern C, D Num_layer 1 00: 1 layer 01: 2layer For(i=0; i<Num_layer;i++){ This loop specifies the Nep for layer 2and above when required for STC. The same Nsch and RCID applied for eachlayer If(H-ARQ Mode = CTC 4 H-ARQ Mode is specified in the H-ARQIncremental Redundancy) compact_UL_Map IE format for Switch H-ARQ Mode{Nep} Elseif (H-ARQ Mode = Generic Chase) {UIUC} } Padding variable }

FIG. 11 illustrates an operation of the CSM method using the HARQ-MAPaccording to an embodiment of the present invention. Table 8 shows adata format of the “MIMO compact UL MAP IE” message.

The “MIMO compact UL MAP IE” message uses a ‘compact UL-MAP IE fornormal subchannel’ for allocating the subchannel and a ‘compact UL-MAPIE for band AMC’ for allocating the band AMC. Because the samesubchannel (uplink resource) should be allocated according tocharacteristics of the CSM, as shown in FIG. 11, the HARQ-MAP uses twoseparate IEs so as to allocate the same subchannel to two terminalshaving a different connection factor (RCID), respectively. Furthermore,in order to allocate a function of the allocated region, the ‘MIMOcompact UL IE for collaborative SM’ is separately attached to a positionsubsequent to the two IEs. A value of ‘CSM_control’ is differentiatedaccording to the number of antennas of each terminal. That is, when eachterminal uses only one antenna, the pilot pattern used by the twoterminals is divided into A and B. When each terminal uses two antennas,A and B are allocated to one terminal and C and D are allocated to theother terminal.

TABLE 8 Size Syntax (bits) Notes MIMO_compact UL-map IE( ){ CompactUL-MAP 3 Type = 7 UL-MAP Sub-type 5 CSM = 0x02 Length 4 Length of the IEin Bytes CSM control 1 For Collaborative SM capable MSS with one antenna0: pilot pattern A 1: pilot pattern B For Collaborative SM capable MSSwith dual antennas 0: pilot pattern A, B 1: pilot pattern C, D Num_layer 1 00: 1 layer 01: 2 layer For(i=0; i<Num_layer;i++){ Thisloop specifies the Nep for layer 2 and above when required for STC. Thesame Nsch and RCID applied for each layer  If(H-ARQ Mode = CTC 4 H-ARQMode is specified in the H-ARQ Incremental Redundancy) compact_UL_Map IEformat for Switch H-ARQ Mode {Nep}  Elseif (H-ARQ Mode = Generic Chase){UIUC} } Padding variable }

Two terminals supporting the CSM method use SM and STTD methods,respectively.

Explaining it briefly, for example, assuming that one terminal using twoantennas transmits data through the same data region, when the terminaluses the SM method, the two antennas simultaneously send signals,respectively, and the base station receives each signal represented by[Equation 6]. Therefore, when the base station detects each signal, apower control is required.

r=h ₁ ·s ₁ +h ₂ ·s ₂ +n  [Equation 6]

When the terminal uses the STTD method, at first (i.e., in time1), thetwo antennas transmit s₁s₂, respectively. Next (i.e., in time2), the twoantennas transmit −s*₂, s*₁, respectively. The signals received in thebase station can be seen in [Equation 7].

r _(time1) =h ₁ ·s ₁ +h ₂ ·s ₂ +n

r _(time2) =h ₁·(−s* ₂)+h ₂ ·s* ₁ +n  [Equation 7]

Here, assuming that noise is as tiny as being ignored, two unknowntransmission signals, as shown in [Equation 8], can be detected by usingtwo known reception signals. As a result, there is not any reason to usespecific power for the detection.

Ŝ ₁ =h* ₁ ·r _(time1) +h ₂ r* _(time2)

Ŝ ₂ =h* ₂ ·r _(time1) +h ₁ ·r* _(tim2)  [Equation 8]

Thus, when two terminals with two antennas transmit data through thesame data region, the CSM method may be used. In other words, four datacan be detected by using power control in the SM method, while fourtransmission signals can be detected by using four reception signals inthe STTD method.

As described above, an uplink capacity can be increased without anadditional frequency bandwidth by embodying a method in which more thantwo users use a radio resource allocated to one user. Furthermore,limited radio resources can be utilized more efficiently by allocating aradio resource, which should have been allocated to an uplink, to adownlink, as assigning parts of time assigned to the uplink to thedownlink in a TDD method.

The present invention can save the uplink radio resource by allocatingthe uplink resource to two terminals, and also be applied to both ancurrent resource allocation and the HARQ.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1-20. (canceled)
 21. A method of allocating a radio resource in awireless communication system utilizing orthogonal frequency divisionmultiplexing, the method comprising: transmitting, to a mobile station,data associated with a radio resource allocation map, wherein the radioallocation map comprises control parameters for transmitting uplink datato the base station, wherein at least one of the control parameterscomprises an orthogonal pilot pattern indicator for using orthogonalpilot patterns associated with supporting dual transmission by at leastone mobile station, the orthogonal pilot patterns comprising a minuspilot and a plus pilot being used for an uplink basic allocation unit;and receiving uplink data from the mobile station, wherein the uplinkdata in the uplink basic allocation unit are at least one of: a firsttile comprising the plus pilot located at a lower left corner of thetile, the minus pilot located at an upper right corner of the tile, anda null subcarrier located at an upper left corner of the tile and alower right corner of the tile; and a second tile comprising the minuspilot located at an upper left corner of the tile, the plus pilotlocated at a lower right corner of the tile, and a null subcarrierlocated at a lower left corner of the tile and an upper right corner ofthe tile.
 22. The method of claim 21, wherein each one of the orthogonalpilot patterns comprises a plus pilot and the minus pilot located ateach diagonal corner of the uplink basic allocation unit.
 23. The methodof claim 22, wherein the plus pilot and the minus pilot have oppositephases.
 24. The method of claim 21, wherein information associated withthe orthogonal pilot patterns is communicated to the mobile stationusing a map information element.
 25. The method of claim 21, whereininformation associated with the orthogonal pilot patterns iscommunicated to the mobile station using a HARQ map information element.26. The method of claim 21, wherein the dual transmission is achieved byusing at least two antennas in the mobile station.
 27. The method ofclaim 21, wherein the uplink data comprises at least two sets of dataspatially multiplexed onto the same subchannel by using the orthogonalpilot patterns.
 28. A method of allocating a radio resource in awireless communication system utilizing orthogonal frequency divisionmultiplexing, the method comprising: transmitting, to a mobile station,data associated with a radio resource allocation map, wherein the radioallocation map comprises an orthogonal pilot pattern indicator for usingorthogonal pilot patterns associated with supporting dual transmissionby at least one mobile station, the orthogonal pilot patterns are atleast one of: a first pilot pattern comprising a plus pilot located at alower left corner of a tile and a minus pilot located at an upper rightcorner of the tile; and a second pilot pattern comprising a minus pilotlocated at an upper left corner of a tile and a plus pilot located at alower right corner of the tile.
 29. The method of claim 28, wherein theplus pilot and the minus pilot have opposite phases.
 30. The method ofclaim 28, wherein information associated with the orthogonal pilotpatterns is communicated to the mobile station using a map informationelement.
 31. The method of claim 28, wherein information associated withthe orthogonal pilot patterns is communicated to the mobile stationusing a HARQ map information element.